Heteroepitaxial growth of 3C-SiC on Si(100) by pulsed supersonic free jets of Si(CH3)(4) and Si3H8 with various mixture ratios has been investigated. The heteroepitaxy is achieved at the substrate temperature of 900 degrees C without any carbonization process. The films grown by pure Si(CH3)(4) contain inverse pyramidal pits surrounded by the {111} planes of Si, while {311} faceted pits are formed by mixing Si(CH3)(4) with a small amount of Si3H8. When the Si3H8/Si(CH3)(4) ratio further increases, pit formation is suppressed and instead Si islands are epitaxially grown from the pit region.